Distribution of Boron in Different Fractions in Some Alkaline Calcareous Soils

Abstract

Distribution of boron (B) in different fractions is still not well defined when it is applied in B-deficient alkaline calcareous soil and after harvesting of the sown crop. In the present greenhouse experiment with green gram crop, three B-deficient soils with calcium carbonate contents of 0.8 (S I), 2.1 (S II), and 4.6 (S III) percent were collected from different sites in Ludhiana and Bhatinda Districts, Punjab, India. The treatments composed of five levels of soil-applied B (0, 0.5, 0.75, 1.0, and 1.5 mg B kg−1) soil and the experiment was laid out in Completely Randomized Design (CRD) factorial design with three replications. Mean readily soluble, specifically adsorbed, and oxide-bound B fractions got increased significantly with increase in B applications. Distribution of readily soluble B was more in low calcareous soil than in high calcareous soil. Mean values of specifically adsorbed, oxide-bound, residual, and total B were significantly more in high calcareous soils as compared to low calcareous soils. At maturity, specifically adsorbed B converted into other fractions to maintain equilibrium in soil solution. Organically bound B was greater than the oxide-bound B fraction. Among all fractions, residual fraction accounted for the major portion of the total B. Available B was negatively and significantly correlated with calcium carbonate (CaCO3) content of soil (r = −0.99*). At the same time, specifically bound B was also negatively and significantly correlated with readily soluble B (r = −0.99*) whereas organically bound B was positively correlated with organic carbon content of soil (r = −0.99*).